Waterhemp and Palmer amaranth plants that have escaped POST applications or emerged after are now starting to develop mature seed.
These plants can produce upwards of one million seeds per plant in certain situations. When it comes to the management of these weeds, the best offense is a good defense.
Anything we can do from now through harvest to prevent seed from being deposited into the soil seed bank will pay dividends down the road.
At this point in the season there are limited options for control beyond scouting and hand pulling. Just a few plants left in the field can lead to a total infestation within a few years. Viability of waterhemp and Palmer amaranth seed is greatly reduced after 3-5 years. Some diligence over a couple of growing seasons can drastically reduce populations.
Aside from tremendous seed production, fast growth rates, and lengthy emergence windows, what makes us most nervous about these weeds is their propensity to develop herbicide resistance.
In other states, waterhemp has exhibited the ability to resist up to seven different herbicide sites of action, and Palmer amaranth can now resist up to nine. Resistance to more than one site of action within a single population is not uncommon. Metabolic herbicide resistance may increase the prevalence of populations with resistance to multiple herbicide groups. To date, Ohio seems to be a bit behind states to the south and west in terms of resistance issues, though experience would tell us it's only a matter of time. The status of herbicide resistance in Ohio waterhemp populations was covered in this article.
OSU weed science has a plethora of resources that can be helpful for scouting, including a pigweed ID guide, pigweed management fact sheet, and YouTube video that covers assessment for seed maturity. More helpful information on the management of pigweeds can be found on the OSU weed science website.
Below are some guidelines from Dr. Mark Loux for late-season scouting from the 2018 newsletter on this topic:
“We recommend the following as we progress from now through crop harvest:
More information is available from Alyssa Essman via email or phone at 614-247-5810.
Click here for more No-Till News.
Get full access NOW to the most comprehensive, powerful and easy-to-use online resource for no-tillage practices. Just one good idea will pay for your subscription hundreds of times over.
Download these helpful knowledge building tools
The 31st annual National No-Tillage Conference offers a mix of general sessions, No-Till Classrooms and invaluable No-Till Roundtables. Just as important is the chance to profit from unlimited hallway networking with the most innovative, forward-thinking minds in no-till during this January's event in St. Louis!
Design, CMS, Hosting & Web Development :: ePublishing